Stabs Errors Compiling Java Classes

Wed Dec 4 18:22:00 GMT 2002

Andrew Haley wrote:
> Ranjit Mathew writes:
> > Andrew Haley wrote:
> > > Ranjit Mathew writes:
> > > > Tom Tromey wrote:
> > > > > Ranjit> 4. description - can be any *16-bit, unsigned value*.
> > > > > Ranjit> (Used for storing line numbers when using GNU debug
> > > > > Ranjit> extensions. Hence a limit of 65535 lines for the
> > > > > Ranjit> source code if stabs debug info is to be used.)
> > > > > 
> > > > > Ok, I think I can explain. In gcj we keep track of both line and
> > > > > column numbers by packing them in to (I believe) a single 32-bit
> > > > > value. Perhaps this is not being properly decoded before it is passed
> > > > > to the debug info generator. That's an area I really know very little
> > > > > about.
> > > > 
> > > > The GCC "tree.h" header file defines EXPR_WFL_* macros that
> > > > encapsulate this behaviour - it would seem by looking at the
> > > > definition of these macros that line/col. info is packed
> > > > in a 20+12 bits packed format respectively, for Java.
> > > > 
> > > > However, in dbxout.c (dbxout_finish_symbol), I've had to
> > > > right shift the packed value *16-bits* to the right to get a
> > > > sane value! Some real SNAFU seems to be happening in there...
> > > 
> > > SNAFU? I don't think so. See this:
> > > 
> > > /* Retrieve those two info separately. */
> > > #define DECL_SOURCE_LINE_FIRST(DECL) (DECL_SOURCE_LINE(DECL) & 0x0000ffff)
> > > #define DECL_SOURCE_LINE_LAST(DECL) (DECL_SOURCE_LINE(DECL) >> 16)
> > 
> > Thanks for pointing that out - that explains the "interesting"
> > observation in my last mail. In dbxout.c, I should really just
> > get the *lower 16-bits* for the first line of the function.
> > 
> > However, I still think there's a SNAFU - why is this
> > encoded line number being passed as is to the back end?
> > The stabs debugging info generator (dbxout.c) certainly
> > seems to be unaware of this encoding. Aren't other
> > debugging formats confused by it?
>> They're not confused, no, because DWARF unsigned integer attributes
> are of type unsigned long. However, IMO the information is incorrect,
> as you say.
>> > And why are there *two* ways of encoding line number
> > information for decl-s - the EXPR_WFL_XXX 20+12 bit
> > line no./col. no. way (gcc/tree.h) and the
> > DECL_SOURCE_LINE_MERGE 16+16 end/begin line no. way
> > (gcc/java/parse.h)? And they both seem to be using the
> > DECL_SOURCE_LINE( ) of a decl... Somewhat confusing for
> > a "nooB"!
>> No. See:
>>> #define EXPR_WFL_SET_LINECOL(NODE, LINE, COL) \
> (EXPR_WFL_LINECOL(NODE) = ((LINE) << 12) | ((COL) & 0xfff))
>> #define EXPR_WFL_LINECOL(NODE) (EXPR_CHECK (NODE)->exp.complexity)
>> #define DECL_SOURCE_LOCATION(NODE) (DECL_CHECK (NODE)->decl.locus)
> #define DECL_SOURCE_LINE(NODE) (DECL_SOURCE_LOCATION (NODE).line)
>>> Try setting DECL_SOURCE_LINE = DECL_SOURCE_LINE_FIRST in
> source_end_java_method() before calling rest_of_compilation().

Yes, that seems to work well. Will you please modify it accordingly?
Or would you like me to submit a patch or open a PR for this?
Ranjit.
-- 
Ranjit Mathew Email: rmathew AT hotmail DOT com
Bangalore,
INDIA. Web: http://ranjitmathew.tripod.com/